Mount St. Helens. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome.ount St. Helens. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome.
Definition of plantar. : of or relating to the sole of the foot plantar wart.
Plantar flexion is the movement which decreases the angle between the sole of the foot and the back of the leg. For example, the movement when depressing a car pedal or standing on the tiptoes can be described as plantar flexion. A ballerina, demonstrating plantar flexion of the feet.